Caswell CopyCad & Zinc plating test 1

1) Test pieces are 2 x 3" mild steel sheet @ 18 ga

2) all Caswell products mixed at recommended ratios.

3) all tests run constant current using B&K Precision, 16v, 10A CV/CC bench supply

4) Parts were first degreased/cleaned, then bead blasted, pre-cleaned w/ Simple green, soaked in 180º SP degreaser for 5 minutes , rinsed , acid pickled for 1 minute (5% muriatic) rinsed, zinc plated at 65º for 15 minutes, rinsed, & blow dried.

Photos 1-4 show results without brightener. 95% of my needs are for unbrightened parts, to be finished w/black conversion coating.

Photos 5-10 are the same pieces, replated with brightener added.

Final surface finishes shown below. Thumbnails link to a full size 1024 wide detailed image.

Table of volts/amps/resistance for photos 1-4

 Volts (measured)

current - Amps

 current density -
mA/sq-in

calculated resistance

 0.232

0.23

24
(9.47" part)

 1.009

0.473

 0.6

 50

 0.788

0.555

 0.9

 75

 0.617

 0.65

 1.2

 100

 0.542

 0.73

 1.5

 125

 0.487
The first test piece had only 9.47 square inces of surface area. That's what was left over after cutting the other pieces. I used it as an afterthought.

This photo was taken at an angle to relect ambient light from cloudy sky.

Best looking of these parts was a toss-up between the 50 & 75 mA parts. I would give a nod the the 50mA part.

The 2 highest current density parts were darker looking than the picture shows, with the obvious streaks.

 

photo 1

 The same pieces taken head-on. The darker color of the right 2 pieces is more noticeable here.

(Ignore the fingerprint on the first piece :-)

photo 2
A closer view of the first 3 pieces.

 

photo 3
and closer of the last 3. The spotting in the upper part of the 125 mA piece convinced me to go no higher in current density.

 

photo 4

Table of volt/amps for photos 5-10

  Volts (measured)

 current - Amps

  current density -
mA/sq-in

 calculated resistance

 0.44

0.3

 25

 1.467

0.585

0.6

 50

 .975

0.7

0.9

 75

 .778

0.83

1.2

 100

 .692

The 4 full size parts were stripped and resused for these tests.

Surprise here! Added brightener resulted in higher voltages across the board, so it must increase electrolyte resistance!

 The 25 mA partcame out w/ a matte finish, rather dull & significanlty less refective than the others, and has a hint of streaking in the center.

What's not clear in the pictures (due to resolution & photographic limitations) is that the graininess of the plate gets slightly coarser as current density goes up.

 

photo 5

This shot, taken head-on, clearly shows the dulnes of the 25 mA plate, and somewhat less-than-complete interior area of the 50 mA part.

The 75 mA parts looks the best of this lot.

 

photo 6
Taken at an oblique angle to try and better highlite the differences.

photo 7

Close ups of the sequential pairs.

Here the 25 & 50 mA parts

photo 8

Here the 50 & 75 mA parts.

One thing that's difficult to notice in the photos, is that the outer edges of the 75 mA part have a smoother & shinier plate. The interior area is rougher.

photo 9

 And the 75 & 100 mA parts.

A big surprise here, the circled corner did not plate! Beginning at about the circle passed the part, plating just faded out to almost nothing at the tip of the corner!

 

photo 10